This makes me wonder if the supervised/unsupervised distinction is useful at all. Maybe you could say instead that all learning algorithms simply need some way

This makes me wonder if the supervised/unsupervised distinction is useful at all. Maybe you could say instead that all learning algorithms simply need some way to measure similarity between the training examples, and it doesn't make a fundamental difference if you cluster examples by their target label ("supervised") or by their input vectors ("unsupervised") or by the context in which they appear (word2vec).